A plasma display panel displays images by exciting a phospher with ultraviolet light generated by gas discharge for light emission.
A plasma display device using such a plasma display panel has a higher display quality than a liquid crystal panel with regard to features including a high-speed display capability, a wide viewing angle, easy upsizing, and a self-luminous property. Thus, the plasma display panel especially attracts attention among flat-panel displays these days, and is used in various applications such as a display device for a location where many people gather or for enjoying a large-screen image at home.
A plasma display panel is roughly classified into an AC type and DC type by driving method, and a surface-discharge type and opposed-discharge type by discharging type. In terms of moving to finer-resolution, increasing size of a screen, and the simplicity of the structure, a plasma display panel with a three-electrode structure, that is, a surface-discharge type and AC type, prevails. An AC-type plasma display panel is composed of a front panel and a back panel. The front panel, which is equipped with display electrodes that are composed of scanning electrodes and sustain electrodes on the front substrate (a glass substrate), forms a first dielectric layer covering the display electrodes. Meanwhile, the back panel, which is equipped with providing at least a plurality of data electrodes that are orthogonal to the display electrodes on the back substrate (a glass substrate), forms a second dielectric layer covering the data electrodes. Arranging the front panel and the back panel as facing each other forms discharge cells at the interception points of the display electrodes and data electrodes, and also provides phospher layers in the discharge cells.
In the structure of such a plasma display panel, an example for a multilayered structure of the first dielectric layer and/or second dielectric layer is disclosed in the FPD Technology Outlook 2001 (Electronic Journal, Co., Oct. 25, 2000, pp. 594–597) for example. Its objective includes using a material with a high glass softening point for the lower layer, and a low glass softening point for the upper layer for example, covering defects such as pinholes that are generated while forming the lower layer, on the upper layer, thereby improving the breakdown voltage. Also, these dielectric layers are formed not in a single coating but in laminating several times for a certain thickness, which will result in a favorable surface roughness.
However, in some cases, although these dielectric layers are formed in the above-mentioned way, convex blisters formed on the surface cause the surface roughness to be unfavorable, or pinholes which are generated decrease the breakdown voltage.
As a result of research on these problems conducted by the present inventor, the following facts have been found. FIGS. 5, 6, and 7 are sectional views schematically illustrating conditions of the end part of the dielectric layer when a dielectric material with such a conventional laminated structure is formed, where the first dielectric layer formed on the front panel is shown as an example. The description is made for an example where, as shown in FIG. 5, on a front substrate 23, a first dielectric layer 27 is composed of two layers, i.e. a lower dielectric layer 27a and an upper dielectric layer 27b. If the upper dielectric layer 27b is formed with the periphery of the lower dielectric layer 27a covered, a bubble 101 is involved between the periphery of the lower dielectric layer 27a and the upper dielectric layer 27b. In such a case, as shown in FIG. 6, this bubble 101 expands in a subsequent baking process, causing a blister 102 to occur on the first dielectric layer 27. In addition, as shown in FIG. 7, burst blisters cause a pinhole 103 to occur on the upper dielectric layer 27b, resulting in a deterioration of the performance of breakdown voltage of first dielectric layer 27. This problem is also found in the second dielectric layer provided in the back panel.
The present invention has been made from these situations and to solve the above problems. Accordingly, an object of the present invention is to implement a plasma display panel enabling a favorable image display and having dielectric layers with a multilayered structure that prevents bubbles from being contained.